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module Data.Text.ParagraphLayout.TextContainer
(TextContainer
,getText
,splitTextAt8
,splitTextsAt8
)
where
import Data.Text (Text)
import Data.Text.Foreign (I8, lengthWord8)
class TextContainer a where
-- | Unwrap text from the container.
getText :: a -> Text
-- | Split a text container at the given number of `Word8` units
-- from its beginning.
splitTextAt8 :: I8 -> a -> (a, a)
splitTextAt8 _ _ = error "container cannot be split"
-- | Treat a list of text containers as a contiguous sequence,
-- and make a split at the given number of `Word8` from the beginning
-- of this sequence.
--
-- If @n@ falls on a container boundary, the total number of output containers
-- will equal the number of input containers; otherwise, it will be one larger.
splitTextsAt8 :: TextContainer a => I8 -> [a] -> ([a], [a])
splitTextsAt8 n rs = (pre, post)
where
pre = reverse rpre
(rpre, post) = splitTextsAt8' n [] rs
splitTextsAt8' :: TextContainer a => I8 -> [a] -> [a] -> ([a], [a])
splitTextsAt8' _ rpre [] = (rpre, [])
splitTextsAt8' n rpre (r:rs)
| n <= 0 = (rpre, r:rs)
| n >= l = splitTextsAt8' (n - l) (r:rpre) (rs)
| otherwise = let (r1, r2) = splitTextAt8 n r in (r1:rpre, r2:rs)
where
l = fromIntegral $ lengthWord8 $ getText r